Advances in technical development and increased demand for mobile appliances have caused a rapid increase in the demand for batteries serving as an energy source, and accordingly, many studies have been conducted on batteries capable of meeting the demand.
Representatively, with regard to the shape of batteries, there is a high demand for angled secondary batteries and pouch type secondary batteries, which are thin and thus may be applied to products such as, for example, portable phones. In addition, from the aspect of materials, there is a high demand for lithium secondary batteries such as, for example, lithium ion batteries and lithium ion polymer batteries, which have a high energy density, discharge voltage, and output stability.
FIG. 1 is an exploded perspective view illustrating a general pouch type secondary battery. The pouch type secondary battery 100 includes an electrode assembly 20, electrode tabs 21 extending from the electrode assembly 20, electrode leads 23 and 24 welded to the electrode tabs 21, and a pouch 30 configured to receive the electrode assembly 20 therein.
Here, the electrode assembly 20 is an electric power generation element in which a positive electrode and a negative electrode are stacked one above another in sequence with a separator interposed therebetween, and has a stack type or stack/folding type configuration. The electrode tabs 21 extend from respective electrode plates of the electrode assembly 20.
In addition, the electrode leads 23 and 24 are electrically connected to the respective electrode tabs 21, which extend from the respective electrode plates, via welding, and portions of the respective electrode leads are exposed outside of the pouch 30. At this time, an insulation film (not illustrated) is attached to portions of the upper and lower surfaces of the electrode leads 23 and 24 in order to increase the efficiency with which the electrode leads are sealed by the pouch 30 and to ensure the electrical insulation thereof.
In addition, the pouch 30 is formed of an aluminum laminate sheet and provides a space in which the electrode assembly 20 may be received.
The pouch type secondary battery has low fixing force because the electrode assembly 20 and the electrode leads 23 and 24 are fixed to a sealing region of the pouch 30, and the electrode assembly 20 may unintentionally move within the pouch 30.
Meanwhile, FIG. 2 is a conceptual view illustrating the arrangement of the electrode tabs and electrode leads when the electrode assembly is seated in the pouch. The positive electrode taps 21 protrude from a positive electrode collector 21a of the electrode assembly 20 and are integrally connected to the positive electrode lead 23 via welding.
The positive electrode lead 23 is sealed by the pouch 30 such that opposite ends 23a thereof connected to positive electrode tap bonds are exposed, and the positive electrode taps 21 are integrally coupled to one another so as to form the bonds. As such, the inner upper end of the pouch 30 is spaced apart from the surface of the upper end of the electrode assembly 20 by a given distance, and the positive electrode taps 21 of the bonds are bent in the direction crossing the extending direction thereof. As illustrated in FIG. 2, the region where the electrode tabs and the electrode lead are coupled has a shape similar to the alphabet letter “V”, and thus is referred to as a V-forming region. With the coupling region of the electrode tabs and the electrode lead, as illustrated in FIG. 1, the inner space of the pouch 30 includes a so-called terrace 40, which is an empty space not occupied by the electrode assembly 20 and the electrode leads 23 and 24.
In a conventional pouch type secondary battery, the electrode assembly 20 easily moves along the interface with a battery case due to the terrace 40, which is an empty space, when the battery falls or receives vibration shocks.
In particular, an electrolyte containing lithium salt, which is injected into the pouch 30, serves as a lubricant at the interface between the electrode assembly 20 and the pouch 30, thereby facilitating movement of the electrode assembly 20. The movement of the electrode assembly 20 causes internal short circuits, attributable to the contact of different electrodes at the V-forming region, ultimately, deteriorating the safety of the battery. Therefore, the manufacture of the pouch type battery requires a solution in order to secure the safety thereof.